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Unread 08-08-2013, 22:53
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Re: Arduino + Ethernet Shield Help

Quote:
Originally Posted by jwallace15 View Post
Then I tried hooking that relay's input pin directly to the Arduino's +5V pin (using the + on a breadboard). Nothing then, either.

I then proceeded to hook all of the inputs from the relay board to the +5V, and none of them worked.

(if needed, this is the link to the manufacturer's website and my product)
System ground the input to turn it on. I will test in the morning.

Yes I quickly tested with DMM. Grounded input lights LED at input.
Testing with a 5V 3A supply reveals that ground on input energizes contact.
NPN transistor in photocoupler to NPN transistor on PCB with 500 Ohm resistor bias.

Input circuit is LED .... opto-isolator LED ... 1k resistor ... Vcc

I bought one cause I could

Watch the jumper in the lower left BTW.
JD-Vcc should be jumpered to Vcc.
Do not put the jumper between GND and Vcc (bad design makes you think that is a storage position).
I guess the plus side is that would be a wonderful place to put an emergency stop button.

Now that I actually have a unit to examine, all the numbers on the drawing and documentation at the Amazon link are wrong. There was no documentation with the board when I got it. The box contains no useful information.

R1, R3, R5, R7, R9, R11, (yes the next 2 are even I have no idea why), R12, R14 are all 1k Ohm on my board.
Make sure to measure yours to be sure.
That limits the current you must sink to turn on a relay to 2.5mA each.
So all 8 inputs activating relays will only sink 20mA.
They get away with this because of the amplifier at the output of the opto-isolator.
So this should operate just fine straight from the Arduino digital I/O pins.

With all the inconsistencies here be sure to check before you assume these boards are identical!

Last edited by techhelpbb : 09-08-2013 at 10:32.